POC: Alembic merge heads for git-flow migration reconciliation

[galvana]

Summary

Proof-of-concept demonstrating that divergent alembic migrations are resolvable when adopting git-flow.

The scenario:

• A hotfix migration lands on main (aaaa11112222)
• A feature migration develops independently on dev (bbbb33334444)
• Both share the same down_revision, creating two alembic heads

The resolution:

• alembic merge heads generates a merge migration (cccc55556666) with down_revision = ("aaaa11112222", "bbbb33334444")
• Single head restored, no data loss, no conflicts

Migration chain:

d6e7f8a9b0c1 (previous head)
     |
     +---> aaaa11112222 (hotfix on main)
     |
     +---> bbbb33334444 (feature on dev)
             \       /
              v     v
        cccc55556666 (merge migration)

Key takeaway: This is a standard alembic feature. The merge migration has no schema changes — it just unifies the revision graph. Can be automated in CI by detecting alembic heads returning >1 result.

⚠️ Not intended to merge. Demo only for the git-flow branching proposal.

Test plan

• Python parses all three migrations correctly
• Chain visualization confirms single head after merge
• (optional) Run alembic upgrade head in a test DB to confirm execution order

🤖 Generated with Claude Code

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
fides-plus-nightly	Ignored		Apr 20, 2026 11:27pm
fides-privacy-center	Ignored		Apr 20, 2026 11:27pm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.05%. Comparing base (b5b98e6) to head (5dffccc).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7976   +/-   ##
=======================================
  Coverage   85.04%   85.05%           
=======================================
  Files         631      631           
  Lines       41213    41213           
  Branches     4807     4807           
=======================================
+ Hits        35049    35053    +4     
+ Misses       5070     5067    -3     
+ Partials     1094     1093    -1     

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